LLVM 17.0.0git
StackSlotColoring.cpp
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1//===- StackSlotColoring.cpp - Stack slot coloring pass. ------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file implements the stack slot coloring pass.
10//
11//===----------------------------------------------------------------------===//
12
13#include "llvm/ADT/BitVector.h"
15#include "llvm/ADT/Statistic.h"
27#include "llvm/CodeGen/Passes.h"
33#include "llvm/Pass.h"
36#include "llvm/Support/Debug.h"
38#include <algorithm>
39#include <cassert>
40#include <cstdint>
41#include <iterator>
42#include <vector>
43
44using namespace llvm;
45
46#define DEBUG_TYPE "stack-slot-coloring"
47
48static cl::opt<bool>
49DisableSharing("no-stack-slot-sharing",
50 cl::init(false), cl::Hidden,
51 cl::desc("Suppress slot sharing during stack coloring"));
52
53static cl::opt<int> DCELimit("ssc-dce-limit", cl::init(-1), cl::Hidden);
54
55STATISTIC(NumEliminated, "Number of stack slots eliminated due to coloring");
56STATISTIC(NumDead, "Number of trivially dead stack accesses eliminated");
57
58namespace {
59
60 class StackSlotColoring : public MachineFunctionPass {
61 LiveStacks* LS;
63 const TargetInstrInfo *TII;
64 const MachineBlockFrequencyInfo *MBFI;
65
66 // SSIntervals - Spill slot intervals.
67 std::vector<LiveInterval*> SSIntervals;
68
69 // SSRefs - Keep a list of MachineMemOperands for each spill slot.
70 // MachineMemOperands can be shared between instructions, so we need
71 // to be careful that renames like [FI0, FI1] -> [FI1, FI2] do not
72 // become FI0 -> FI1 -> FI2.
74
75 // OrigAlignments - Alignments of stack objects before coloring.
76 SmallVector<Align, 16> OrigAlignments;
77
78 // OrigSizes - Sizes of stack objects before coloring.
80
81 // AllColors - If index is set, it's a spill slot, i.e. color.
82 // FIXME: This assumes PEI locate spill slot with smaller indices
83 // closest to stack pointer / frame pointer. Therefore, smaller
84 // index == better color. This is per stack ID.
86
87 // NextColor - Next "color" that's not yet used. This is per stack ID.
88 SmallVector<int, 2> NextColors = { -1 };
89
90 // UsedColors - "Colors" that have been assigned. This is per stack ID
92
93 // Assignments - Color to intervals mapping.
95
96 public:
97 static char ID; // Pass identification
98
99 StackSlotColoring() : MachineFunctionPass(ID) {
101 }
102
103 void getAnalysisUsage(AnalysisUsage &AU) const override {
104 AU.setPreservesCFG();
112 }
113
114 bool runOnMachineFunction(MachineFunction &MF) override;
115
116 private:
117 void InitializeSlots();
118 void ScanForSpillSlotRefs(MachineFunction &MF);
119 bool OverlapWithAssignments(LiveInterval *li, int Color) const;
120 int ColorSlot(LiveInterval *li);
121 bool ColorSlots(MachineFunction &MF);
122 void RewriteInstruction(MachineInstr &MI, SmallVectorImpl<int> &SlotMapping,
123 MachineFunction &MF);
124 bool RemoveDeadStores(MachineBasicBlock* MBB);
125 };
126
127} // end anonymous namespace
128
129char StackSlotColoring::ID = 0;
130
131char &llvm::StackSlotColoringID = StackSlotColoring::ID;
132
134 "Stack Slot Coloring", false, false)
139 "Stack Slot Coloring", false, false)
140
141namespace {
142
143// IntervalSorter - Comparison predicate that sort live intervals by
144// their weight.
147 return LHS->weight() > RHS->weight();
148 }
149};
150
151} // end anonymous namespace
152
153/// ScanForSpillSlotRefs - Scan all the machine instructions for spill slot
154/// references and update spill slot weights.
155void StackSlotColoring::ScanForSpillSlotRefs(MachineFunction &MF) {
156 SSRefs.resize(MFI->getObjectIndexEnd());
157
158 // FIXME: Need the equivalent of MachineRegisterInfo for frameindex operands.
159 for (MachineBasicBlock &MBB : MF) {
160 for (MachineInstr &MI : MBB) {
161 for (const MachineOperand &MO : MI.operands()) {
162 if (!MO.isFI())
163 continue;
164 int FI = MO.getIndex();
165 if (FI < 0)
166 continue;
167 if (!LS->hasInterval(FI))
168 continue;
169 LiveInterval &li = LS->getInterval(FI);
170 if (!MI.isDebugInstr())
172 LiveIntervals::getSpillWeight(false, true, MBFI, MI));
173 }
174 for (MachineInstr::mmo_iterator MMOI = MI.memoperands_begin(),
175 EE = MI.memoperands_end();
176 MMOI != EE; ++MMOI) {
177 MachineMemOperand *MMO = *MMOI;
178 if (const FixedStackPseudoSourceValue *FSV =
179 dyn_cast_or_null<FixedStackPseudoSourceValue>(
180 MMO->getPseudoValue())) {
181 int FI = FSV->getFrameIndex();
182 if (FI >= 0)
183 SSRefs[FI].push_back(MMO);
184 }
185 }
186 }
187 }
188}
189
190/// InitializeSlots - Process all spill stack slot liveintervals and add them
191/// to a sorted (by weight) list.
192void StackSlotColoring::InitializeSlots() {
193 int LastFI = MFI->getObjectIndexEnd();
194
195 // There is always at least one stack ID.
196 AllColors.resize(1);
197 UsedColors.resize(1);
198
199 OrigAlignments.resize(LastFI);
200 OrigSizes.resize(LastFI);
201 AllColors[0].resize(LastFI);
202 UsedColors[0].resize(LastFI);
203 Assignments.resize(LastFI);
204
205 using Pair = std::iterator_traits<LiveStacks::iterator>::value_type;
206
207 SmallVector<Pair *, 16> Intervals;
208
209 Intervals.reserve(LS->getNumIntervals());
210 for (auto &I : *LS)
211 Intervals.push_back(&I);
212 llvm::sort(Intervals,
213 [](Pair *LHS, Pair *RHS) { return LHS->first < RHS->first; });
214
215 // Gather all spill slots into a list.
216 LLVM_DEBUG(dbgs() << "Spill slot intervals:\n");
217 for (auto *I : Intervals) {
218 LiveInterval &li = I->second;
219 LLVM_DEBUG(li.dump());
220 int FI = Register::stackSlot2Index(li.reg());
221 if (MFI->isDeadObjectIndex(FI))
222 continue;
223
224 SSIntervals.push_back(&li);
225 OrigAlignments[FI] = MFI->getObjectAlign(FI);
226 OrigSizes[FI] = MFI->getObjectSize(FI);
227
228 auto StackID = MFI->getStackID(FI);
229 if (StackID != 0) {
230 AllColors.resize(StackID + 1);
231 UsedColors.resize(StackID + 1);
232 AllColors[StackID].resize(LastFI);
233 UsedColors[StackID].resize(LastFI);
234 }
235
236 AllColors[StackID].set(FI);
237 }
238 LLVM_DEBUG(dbgs() << '\n');
239
240 // Sort them by weight.
241 llvm::stable_sort(SSIntervals, IntervalSorter());
242
243 NextColors.resize(AllColors.size());
244
245 // Get first "color".
246 for (unsigned I = 0, E = AllColors.size(); I != E; ++I)
247 NextColors[I] = AllColors[I].find_first();
248}
249
250/// OverlapWithAssignments - Return true if LiveInterval overlaps with any
251/// LiveIntervals that have already been assigned to the specified color.
252bool
253StackSlotColoring::OverlapWithAssignments(LiveInterval *li, int Color) const {
254 const SmallVectorImpl<LiveInterval *> &OtherLIs = Assignments[Color];
255 for (unsigned i = 0, e = OtherLIs.size(); i != e; ++i) {
256 LiveInterval *OtherLI = OtherLIs[i];
257 if (OtherLI->overlaps(*li))
258 return true;
259 }
260 return false;
261}
262
263/// ColorSlot - Assign a "color" (stack slot) to the specified stack slot.
264int StackSlotColoring::ColorSlot(LiveInterval *li) {
265 int Color = -1;
266 bool Share = false;
267 int FI = Register::stackSlot2Index(li->reg());
268 uint8_t StackID = MFI->getStackID(FI);
269
270 if (!DisableSharing) {
271
272 // Check if it's possible to reuse any of the used colors.
273 Color = UsedColors[StackID].find_first();
274 while (Color != -1) {
275 if (!OverlapWithAssignments(li, Color)) {
276 Share = true;
277 ++NumEliminated;
278 break;
279 }
280 Color = UsedColors[StackID].find_next(Color);
281 }
282 }
283
284 if (Color != -1 && MFI->getStackID(Color) != MFI->getStackID(FI)) {
285 LLVM_DEBUG(dbgs() << "cannot share FIs with different stack IDs\n");
286 Share = false;
287 }
288
289 // Assign it to the first available color (assumed to be the best) if it's
290 // not possible to share a used color with other objects.
291 if (!Share) {
292 assert(NextColors[StackID] != -1 && "No more spill slots?");
293 Color = NextColors[StackID];
294 UsedColors[StackID].set(Color);
295 NextColors[StackID] = AllColors[StackID].find_next(NextColors[StackID]);
296 }
297
298 assert(MFI->getStackID(Color) == MFI->getStackID(FI));
299
300 // Record the assignment.
301 Assignments[Color].push_back(li);
302 LLVM_DEBUG(dbgs() << "Assigning fi#" << FI << " to fi#" << Color << "\n");
303
304 // Change size and alignment of the allocated slot. If there are multiple
305 // objects sharing the same slot, then make sure the size and alignment
306 // are large enough for all.
307 Align Alignment = OrigAlignments[FI];
308 if (!Share || Alignment > MFI->getObjectAlign(Color))
309 MFI->setObjectAlignment(Color, Alignment);
310 int64_t Size = OrigSizes[FI];
311 if (!Share || Size > MFI->getObjectSize(Color))
312 MFI->setObjectSize(Color, Size);
313 return Color;
314}
315
316/// Colorslots - Color all spill stack slots and rewrite all frameindex machine
317/// operands in the function.
318bool StackSlotColoring::ColorSlots(MachineFunction &MF) {
319 unsigned NumObjs = MFI->getObjectIndexEnd();
321 SmallVector<float, 16> SlotWeights(NumObjs, 0.0);
322 SmallVector<SmallVector<int, 4>, 16> RevMap(NumObjs);
323 BitVector UsedColors(NumObjs);
324
325 LLVM_DEBUG(dbgs() << "Color spill slot intervals:\n");
326 bool Changed = false;
327 for (LiveInterval *li : SSIntervals) {
328 int SS = Register::stackSlot2Index(li->reg());
329 int NewSS = ColorSlot(li);
330 assert(NewSS >= 0 && "Stack coloring failed?");
331 SlotMapping[SS] = NewSS;
332 RevMap[NewSS].push_back(SS);
333 SlotWeights[NewSS] += li->weight();
334 UsedColors.set(NewSS);
335 Changed |= (SS != NewSS);
336 }
337
338 LLVM_DEBUG(dbgs() << "\nSpill slots after coloring:\n");
339 for (LiveInterval *li : SSIntervals) {
340 int SS = Register::stackSlot2Index(li->reg());
341 li->setWeight(SlotWeights[SS]);
342 }
343 // Sort them by new weight.
344 llvm::stable_sort(SSIntervals, IntervalSorter());
345
346#ifndef NDEBUG
347 for (LiveInterval *li : SSIntervals)
348 LLVM_DEBUG(li->dump());
349 LLVM_DEBUG(dbgs() << '\n');
350#endif
351
352 if (!Changed)
353 return false;
354
355 // Rewrite all MachineMemOperands.
356 for (unsigned SS = 0, SE = SSRefs.size(); SS != SE; ++SS) {
357 int NewFI = SlotMapping[SS];
358 if (NewFI == -1 || (NewFI == (int)SS))
359 continue;
360
361 const PseudoSourceValue *NewSV = MF.getPSVManager().getFixedStack(NewFI);
362 SmallVectorImpl<MachineMemOperand *> &RefMMOs = SSRefs[SS];
363 for (unsigned i = 0, e = RefMMOs.size(); i != e; ++i)
364 RefMMOs[i]->setValue(NewSV);
365 }
366
367 // Rewrite all MO_FrameIndex operands. Look for dead stores.
368 for (MachineBasicBlock &MBB : MF) {
369 for (MachineInstr &MI : MBB)
370 RewriteInstruction(MI, SlotMapping, MF);
371 RemoveDeadStores(&MBB);
372 }
373
374 // Delete unused stack slots.
375 for (int StackID = 0, E = AllColors.size(); StackID != E; ++StackID) {
376 int NextColor = NextColors[StackID];
377 while (NextColor != -1) {
378 LLVM_DEBUG(dbgs() << "Removing unused stack object fi#" << NextColor << "\n");
379 MFI->RemoveStackObject(NextColor);
380 NextColor = AllColors[StackID].find_next(NextColor);
381 }
382 }
383
384 return true;
385}
386
387/// RewriteInstruction - Rewrite specified instruction by replacing references
388/// to old frame index with new one.
389void StackSlotColoring::RewriteInstruction(MachineInstr &MI,
391 MachineFunction &MF) {
392 // Update the operands.
393 for (MachineOperand &MO : MI.operands()) {
394 if (!MO.isFI())
395 continue;
396 int OldFI = MO.getIndex();
397 if (OldFI < 0)
398 continue;
399 int NewFI = SlotMapping[OldFI];
400 if (NewFI == -1 || NewFI == OldFI)
401 continue;
402
403 assert(MFI->getStackID(OldFI) == MFI->getStackID(NewFI));
404 MO.setIndex(NewFI);
405 }
406
407 // The MachineMemOperands have already been updated.
408}
409
410/// RemoveDeadStores - Scan through a basic block and look for loads followed
411/// by stores. If they're both using the same stack slot, then the store is
412/// definitely dead. This could obviously be much more aggressive (consider
413/// pairs with instructions between them), but such extensions might have a
414/// considerable compile time impact.
415bool StackSlotColoring::RemoveDeadStores(MachineBasicBlock* MBB) {
416 // FIXME: This could be much more aggressive, but we need to investigate
417 // the compile time impact of doing so.
418 bool changed = false;
419
421
423 I != E; ++I) {
424 if (DCELimit != -1 && (int)NumDead >= DCELimit)
425 break;
426 int FirstSS, SecondSS;
427 if (TII->isStackSlotCopy(*I, FirstSS, SecondSS) && FirstSS == SecondSS &&
428 FirstSS != -1) {
429 ++NumDead;
430 changed = true;
431 toErase.push_back(&*I);
432 continue;
433 }
434
435 MachineBasicBlock::iterator NextMI = std::next(I);
436 MachineBasicBlock::iterator ProbableLoadMI = I;
437
438 unsigned LoadReg = 0;
439 unsigned StoreReg = 0;
440 unsigned LoadSize = 0;
441 unsigned StoreSize = 0;
442 if (!(LoadReg = TII->isLoadFromStackSlot(*I, FirstSS, LoadSize)))
443 continue;
444 // Skip the ...pseudo debugging... instructions between a load and store.
445 while ((NextMI != E) && NextMI->isDebugInstr()) {
446 ++NextMI;
447 ++I;
448 }
449 if (NextMI == E) continue;
450 if (!(StoreReg = TII->isStoreToStackSlot(*NextMI, SecondSS, StoreSize)))
451 continue;
452 if (FirstSS != SecondSS || LoadReg != StoreReg || FirstSS == -1 ||
453 LoadSize != StoreSize)
454 continue;
455
456 ++NumDead;
457 changed = true;
458
459 if (NextMI->findRegisterUseOperandIdx(LoadReg, true, nullptr) != -1) {
460 ++NumDead;
461 toErase.push_back(&*ProbableLoadMI);
462 }
463
464 toErase.push_back(&*NextMI);
465 ++I;
466 }
467
468 for (MachineInstr *MI : toErase)
469 MI->eraseFromParent();
470
471 return changed;
472}
473
474bool StackSlotColoring::runOnMachineFunction(MachineFunction &MF) {
475 LLVM_DEBUG({
476 dbgs() << "********** Stack Slot Coloring **********\n"
477 << "********** Function: " << MF.getName() << '\n';
478 });
479
480 if (skipFunction(MF.getFunction()))
481 return false;
482
483 MFI = &MF.getFrameInfo();
485 LS = &getAnalysis<LiveStacks>();
486 MBFI = &getAnalysis<MachineBlockFrequencyInfo>();
487
488 bool Changed = false;
489
490 unsigned NumSlots = LS->getNumIntervals();
491 if (NumSlots == 0)
492 // Nothing to do!
493 return false;
494
495 // If there are calls to setjmp or sigsetjmp, don't perform stack slot
496 // coloring. The stack could be modified before the longjmp is executed,
497 // resulting in the wrong value being used afterwards. (See
498 // <rdar://problem/8007500>.)
499 if (MF.exposesReturnsTwice())
500 return false;
501
502 // Gather spill slot references
503 ScanForSpillSlotRefs(MF);
504 InitializeSlots();
505 Changed = ColorSlots(MF);
506
507 for (int &Next : NextColors)
508 Next = -1;
509
510 SSIntervals.clear();
511 for (unsigned i = 0, e = SSRefs.size(); i != e; ++i)
512 SSRefs[i].clear();
513 SSRefs.clear();
514 OrigAlignments.clear();
515 OrigSizes.clear();
516 AllColors.clear();
517 UsedColors.clear();
518 for (unsigned i = 0, e = Assignments.size(); i != e; ++i)
519 Assignments[i].clear();
520 Assignments.clear();
521
522 return Changed;
523}
MachineBasicBlock & MBB
This file implements the BitVector class.
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
#define LLVM_DEBUG(X)
Definition: Debug.h:101
uint64_t Size
const HexagonInstrInfo * TII
IRTranslator LLVM IR MI
#define I(x, y, z)
Definition: MD5.cpp:58
#define INITIALIZE_PASS_DEPENDENCY(depName)
Definition: PassSupport.h:55
#define INITIALIZE_PASS_END(passName, arg, name, cfg, analysis)
Definition: PassSupport.h:59
#define INITIALIZE_PASS_BEGIN(passName, arg, name, cfg, analysis)
Definition: PassSupport.h:52
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
This file defines the SmallVector class.
Stack Slot Coloring
static cl::opt< bool > DisableSharing("no-stack-slot-sharing", cl::init(false), cl::Hidden, cl::desc("Suppress slot sharing during stack coloring"))
#define DEBUG_TYPE
static cl::opt< int > DCELimit("ssc-dce-limit", cl::init(-1), cl::Hidden)
This file defines the 'Statistic' class, which is designed to be an easy way to expose various metric...
#define STATISTIC(VARNAME, DESC)
Definition: Statistic.h:167
Value * RHS
Value * LHS
Represent the analysis usage information of a pass.
AnalysisUsage & addPreservedID(const void *ID)
AnalysisUsage & addRequired()
AnalysisUsage & addPreserved()
Add the specified Pass class to the set of analyses preserved by this pass.
void setPreservesCFG()
This function should be called by the pass, iff they do not:
Definition: Pass.cpp:265
A specialized PseudoSourceValue for holding FixedStack values, which must include a frame index.
unsigned isStoreToStackSlot(const MachineInstr &MI, int &FrameIndex) const override
If the specified machine instruction is a direct store to a stack slot, return the virtual or physica...
unsigned isLoadFromStackSlot(const MachineInstr &MI, int &FrameIndex) const override
TargetInstrInfo overrides.
LiveInterval - This class represents the liveness of a register, or stack slot.
Definition: LiveInterval.h:686
float weight() const
Definition: LiveInterval.h:718
Register reg() const
Definition: LiveInterval.h:717
void incrementWeight(float Inc)
Definition: LiveInterval.h:719
void setWeight(float Value)
Definition: LiveInterval.h:720
static float getSpillWeight(bool isDef, bool isUse, const MachineBlockFrequencyInfo *MBFI, const MachineInstr &MI)
Calculate the spill weight to assign to a single instruction.
bool overlaps(const LiveRange &other) const
overlaps - Return true if the intersection of the two live ranges is not empty.
Definition: LiveInterval.h:448
MachineBlockFrequencyInfo pass uses BlockFrequencyInfoImpl implementation to estimate machine basic b...
The MachineFrameInfo class represents an abstract stack frame until prolog/epilog code is inserted.
void setObjectSize(int ObjectIdx, int64_t Size)
Change the size of the specified stack object.
Align getObjectAlign(int ObjectIdx) const
Return the alignment of the specified stack object.
int64_t getObjectSize(int ObjectIdx) const
Return the size of the specified object.
void RemoveStackObject(int ObjectIdx)
Remove or mark dead a statically sized stack object.
int getObjectIndexEnd() const
Return one past the maximum frame object index.
uint8_t getStackID(int ObjectIdx) const
void setObjectAlignment(int ObjectIdx, Align Alignment)
setObjectAlignment - Change the alignment of the specified stack object.
bool isDeadObjectIndex(int ObjectIdx) const
Returns true if the specified index corresponds to a dead object.
MachineFunctionPass - This class adapts the FunctionPass interface to allow convenient creation of pa...
void getAnalysisUsage(AnalysisUsage &AU) const override
getAnalysisUsage - Subclasses that override getAnalysisUsage must call this.
virtual bool runOnMachineFunction(MachineFunction &MF)=0
runOnMachineFunction - This method must be overloaded to perform the desired machine code transformat...
PseudoSourceValueManager & getPSVManager() const
const TargetSubtargetInfo & getSubtarget() const
getSubtarget - Return the subtarget for which this machine code is being compiled.
StringRef getName() const
getName - Return the name of the corresponding LLVM function.
bool exposesReturnsTwice() const
exposesReturnsTwice - Returns true if the function calls setjmp or any other similar functions with a...
MachineFrameInfo & getFrameInfo()
getFrameInfo - Return the frame info object for the current function.
Function & getFunction()
Return the LLVM function that this machine code represents.
Representation of each machine instruction.
Definition: MachineInstr.h:68
A description of a memory reference used in the backend.
const PseudoSourceValue * getPseudoValue() const
MachineOperand class - Representation of each machine instruction operand.
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
const PseudoSourceValue * getFixedStack(int FI)
Return a pseudo source value referencing a fixed stack frame entry, e.g., a spill slot.
Special value supplied for machine level alias analysis.
static int stackSlot2Index(Register Reg)
Compute the frame index from a register value representing a stack slot.
Definition: Register.h:52
SlotIndexes pass.
Definition: SlotIndexes.h:319
size_t size() const
Definition: SmallVector.h:91
This class consists of common code factored out of the SmallVector class to reduce code duplication b...
Definition: SmallVector.h:577
void reserve(size_type N)
Definition: SmallVector.h:667
void resize(size_type N)
Definition: SmallVector.h:642
void push_back(const T &Elt)
Definition: SmallVector.h:416
This is a 'vector' (really, a variable-sized array), optimized for the case when the array is small.
Definition: SmallVector.h:1200
TargetInstrInfo - Interface to description of machine instruction set.
virtual const TargetInstrInfo * getInstrInfo() const
unsigned ID
LLVM IR allows to use arbitrary numbers as calling convention identifiers.
Definition: CallingConv.h:24
@ SS
Definition: X86.h:202
initializer< Ty > init(const Ty &Val)
Definition: CommandLine.h:445
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
void stable_sort(R &&Range)
Definition: STLExtras.h:1948
void initializeStackSlotColoringPass(PassRegistry &)
char & MachineDominatorsID
MachineDominators - This pass is a machine dominators analysis pass.
void sort(IteratorTy Start, IteratorTy End)
Definition: STLExtras.h:1683
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:163
char & StackSlotColoringID
StackSlotColoring - This pass performs stack slot coloring.
bool operator()(LiveInterval *LHS, LiveInterval *RHS) const
This struct is a compact representation of a valid (non-zero power of two) alignment.
Definition: Alignment.h:39
This struct contains the mappings from the slot numbers to unnamed metadata nodes,...
Definition: SlotMapping.h:32